# Q. When a certain number is multiplied by 7, the product entirely comprises ones only (1111…). What is the smallest such number?

(a) 15713

(b) 15723

(c) 15783

(d) 15873

Correct Answer: (d) 15873

#### Question from UPSC Prelims 2021 CSAT Paper

**Explanation : **

Best Method- Check All option

15873 × 7 = 111111